1. Field of the Invention
The invention is a bicycle fork with improved steer tube and crown for a bicycle with improved steer tube and crown strength and durability.
2. Description of Related Art
Generally, prior art bicycle fork solutions have included the metal fork with a strong-crown, and a steer tube on the top, with tubular fork blades ending in dropouts. Fiber reinforced plastic composite forks have generally used the strong-crown and blade model, or have molded two halves, with the blades extending into the steer tube area, but being subdivided in halves, that were bonded together.
Foret U.S. Pat. No. 4,828,285, Hollingsworth U.S. Pat. No. 5,016,895 and Buckmiller U.S. Pat. No. 5,609,349 are representative of the high-strength crown approach, although Foret shows the blade halves as an alternative embodiment.
Klein U.S. Pat. Nos. 5,944,932 and 5,692,764 and Bezin U.S. Pat. Nos. 5,039,470 and 5,181,732 are representative of the two blade halves approach. In each approach to a composite fork, separate metal dropouts are used for wheel attachment, primarily because of wear considerations.
An example of a threadless fork and handlebar stem combination is shown in Edwards, U.S. Pat. No. 5,865,069.
Application Publication No. US-2005-0012299-A1, sharing a common assignee herewith, teaches a solution to strengthening the steer tube crown intersection using continuous carbon reinforcing fibers extending from the fork blades, through the crown and into the steer tube. In the fork in this published application, the aluminum steer tube slips over the carbon steer tube and stops short of the crown. The choice of aluminum provides advantages over a fork made entirely of fiber reinforced plastic in that the handlebar stem can be more readily fastened to the steer tube which can be particularly advantageous in situation such as a workshop by a mechanic unskilled in fastening techniques for more exotic materials. The material properties of a metal or other ductile material in the steer tube, in combination with high modulus fiber reinforcement in the fork body yield improvements under certain conditions.
Colegrove, et al, U.S. Pat. No. 6,924,021 describes a complex-shaped carbon fiber structural member and its method of manufacture, using a combination of prepreg sheets, laminations, unidirectional fiber ropes and fiber bundles, which methods can be used in forming the fork of the present invention.
Notable in composite bicycle frame patents is the fact that the disclosures in the leading patents focus on the frame itself, to the exclusion of the fork. Thus, Nelson U.S. Pat. No. 6,270,104 B1, Duplessis U.S. Pat. No. 5,076,601, Trimble U.S. Pat. No. 5,158,733, Brezina U.S. Pat. No. 4,493,749 and Derujinsky U.S. Pat. No. 4,900,048 do not show forks, while Trimble U.S. Pat. Nos. 4,923,203 and 4,982,975 show forks, but only as part of the environment.
The aforementioned patents and application are incorporated by reference as if fully set forth herein.